Basic concepts of the machine parts section. Machine parts: concept and their characteristics

Development modern society differs from ancient themes that people invented and learned to use various kinds of machines. Now even the most remote villages and the most backward tribes are enjoying the fruits of technological progress. Our whole life is accompanied by the use of technology.

In the process of development of society, with the mechanization of production and transport, and the increase in the complexity of structures, the need arose not only unconsciously, but also scientifically, to approach the production and operation of machines.

Since the middle of the 19th century, at Western universities, and a little later at St. Petersburg University, an independent course “Machine Parts” has been introduced into teaching. Today, without this course, training a mechanical engineer of any specialty is unthinkable.

The process of training engineers around the world has a unified structure:

1. In the first courses, fundamental sciences are introduced, which provide knowledge about the general laws and principles of our world: physics, chemistry, mathematics, computer science, theoretical mechanics, philosophy, political science, psychology, economics, history, etc.
2. Then applied sciences begin to be studied, which explain the operation of the fundamental laws of nature in particular spheres of life. For example, technical thermodynamics, strength theory, materials science, strength of materials, computer technology, etc.
3. Starting from the 3rd year, students begin to study general technical sciences, such as “Machine Parts”, “Fundamentals of Standardization”, “Material Processing Technology”, etc.
4. Finally, special disciplines are introduced, when the qualifications of an engineer in the relevant specialty are determined.

The academic discipline "Machine Parts" aims to study by students the designs of parts and mechanisms of devices and installations; physical principles of operation of instruments, physical installations and technological equipment, used in the nuclear industry; design methods and calculations, as well as methods for preparing design documentation. In order to be ready to comprehend this discipline, you must have basic knowledge, which is taught in the courses “Physics of Strength and Strength of Materials”, “Fundamentals of Materials Science”, “Engineering Graphics”, “Computer Science and Information Technology”.

The subject "Machine Parts" is mandatory and basic for courses that involve a course project and diploma design.

Machine parts as a scientific discipline considers the following main functional groups.

1. Body parts, supporting mechanisms and other machine components: plates supporting machines, consisting of individual units; frames carrying the main components of machines; frames transport vehicles; housings of rotary machines (turbines, pumps, electric motors); cylinders and cylinder blocks; gearbox housings; tables, slides, supports, consoles, brackets, etc.
2. Transmissions are mechanisms that transmit mechanical energy over a distance, as a rule, with the transformation of speeds and moments, sometimes with the transformation of types and laws of motion. Rotary motion transmissions, in turn, are divided according to the principle of operation into gear transmissions that operate without slipping - gear transmissions, worm gears and chain transmissions, and friction transmissions - belt transmissions and friction transmissions with rigid links. Based on the presence of an intermediate flexible link, which allows for significant distances between the shafts, a distinction is made between flexible transmissions (belt and chain) and direct contact transmissions (gear, worm, friction, etc.). According to the relative arrangement of the shafts - transmissions with parallel axes of shafts (cylindrical gears, chain, belt), with intersecting axes (bevel gears), with intersecting axes (worm, hypoid). According to the main kinematic characteristic - the gear ratio - a distinction is made between gears with a constant gear ratio(reducing, increasing) and with a variable gear ratio - step (gearboxes) and stepless (variators). Transmissions transforming rotational movement into continuous translational or vice versa, they are divided into gears: screw - nut (sliding and rolling), rack - rack and pinion, rack - worm, long half-nut - worm.
3. Shafts and axles serve to support rotating machine parts. There are gear shafts, load-bearing parts gears - gears, pulleys, sprockets, and main and special shafts that, in addition to gear parts, carry the working parts of engines or machine tools. Axes, rotating and stationary, are widely used in transport vehicles for supporting, for example, non-driving wheels. Rotating shafts or axes rest on bearings, and translationally moving parts (tables, supports, etc.) move along guides. Rolling bearings are most often used in machines; they are manufactured in a wide range of outer diameters from one millimeter to several meters and weighing from fractions of a gram to several tons.
4. Couplings are used to connect the shafts. This function can be combined with compensation for manufacturing and assembly errors, mitigation of dynamic effects, control, etc.
5. Elastic elements are intended to insulate vibrations and dampen impact energy, to perform engine functions (for example, clock springs), to create gaps and tension in mechanisms. There are coil springs, coil springs, leaf springs, rubber springs, etc.
6. Connecting parts are a separate functional group. There are: permanent connections that do not allow separation without destruction of parts, connecting elements or connecting layer - welded, soldered, riveted, adhesive, rolled; detachable connections that allow separation and are carried out by the mutual direction of the parts and friction forces or only by the mutual direction. According to the shape of the connecting surfaces, connections are distinguished by planes and by surfaces of rotation - cylindrical or conical (shaft-hub). Welded joints are widely used in mechanical engineering. From detachable connections greatest distribution received threaded connections made with screws, bolts, studs, nuts.

So, “Machine Parts” is a course in which they study the basics of designing machines and mechanisms.

What are the stages of developing the design of a device, device, installation?

First, a design specification is set, which is the source document for the development of a device, instrument or installation, which specifies:

a) purpose and scope of use of the product; b) operating conditions; c) technical requirements; d) development stage; e) type of production, etc.

Technical task may have an application containing drawings, sketches, diagrams and other necessary documents.

Part technical requirements includes: a) purpose indicators that determine the intended use and application of the device (measurement range, force, power, pressure, sensitivity, etc.; b) the composition of the device and design requirements (dimensions, weight, use of modules, etc.; c) requirements to means of protection (from ionizing radiation, high temperatures, electromagnetic fields, moisture, aggressive environment, etc.), interchangeability and reliability, manufacturability and metrological support; d) aesthetic and ergonomic requirements; d) additional requirements.

The regulatory framework for design includes: a) unified system design documentation; b) a unified system of technological documentation c) State standard RF on the system of development and production of products SRPP - GOST R 15.000 - 94, GOST R 15.011 - 96. SRPP

Any machine, mechanism or device consists of individual parts combined into assembly units.

A part is a part of a machine whose production does not require assembly operations. In terms of their geometric shape, parts can be simple (nuts, keys, etc.) or complex (case parts, machine beds, etc.).

An assembly unit (assembly) is a product whose components are to be connected to each other by screwing, welding, riveting, gluing, etc. Parts included in individual assembly units, are connected to each other movably or immovably.

From the wide variety of parts used in machines for various purposes, we can highlight those that are found in almost all machines. These parts (bolts, shafts, gear parts, etc.) are called parts general purpose and are the subject of the course “Machine Parts”.

Other parts that are specific to a certain type of machine (pistons, turbine blades, propellers, etc.) are called parts special purpose and are studied in relevant special disciplines.

The course "Machine Parts" establishes General requirements requirements for the design of machine parts. These requirements must be taken into account when designing and manufacturing various machines.

The perfection of the design of machine parts is assessed by their performance and efficiency. Performance combines requirements such as strength, rigidity, wear resistance and heat resistance. Profitability is determined by the cost of the machine or its individual parts and operating costs. Therefore, the main requirements to ensure efficiency are minimal weight, simplicity of design, high manufacturability, use of non-scarce materials, high mechanical efficiency and compliance with standards.

In addition, the “Machine Parts” course provides recommendations on the selection of materials for the manufacture of machine parts. The choice of materials depends on the purpose of the machine, the purpose of the parts, methods of their manufacture and a number of other factors. Right choice material significantly affects the quality of the part and the machine as a whole.

Connections of parts in machines are divided into two main groups - movable and fixed. Movable joints are used to ensure relative rotational, translational or complex movement of parts. Fixed connections are designed for rigidly fastening parts together or for installing machines on bases and foundations. Fixed connections can be detachable or permanent.

Detachable connections (bolt, key, gear, etc.) allow repeated assembly and disassembly without destroying the connecting parts.

Permanent connections (rivet, welded, adhesive, etc.) can only be disassembled by destroying the connecting elements - rivets, welds, etc.

Let's consider detachable connections.

By car is a device created by a person that performs mechanical movements to transform energy, materials and information with the aim of completely replacing or facilitating the physical and mental labor of a person, increasing his productivity.

Materials refer to objects being processed, loads being moved, etc.

The car is characterized by the following features:

conversion of energy into mechanical work or conversion of mechanical work into another type of energy;

certainty of movement of all its parts for a given movement of one part;

artificiality of origin as a result of human labor.

According to the nature of the work process, all machines can be divided into classes:

machines - engines. These are energy machines designed to convert energy of any kind (electrical, thermal, etc.) into mechanical energy (solid);

machines - converters - energy machines designed to convert mechanical energy into energy of any kind (electric generators, air and hydraulic pumps etc.);

transport vehicles;

technological machines;

information machines.

All machines and mechanisms consist of parts, assemblies, and assemblies.

Detail- a part of a machine made from a homogeneous material without the use of assembly operations.

Knot- a completed assembly unit that consists of a number of connected parts. For example: bearing, coupling.

Mechanism is an artificially created system of bodies designed to convert the movement of one or more bodies into the required movements of other bodies.

Machine requirements:

High performance;

2. Recoupment of design and manufacturing costs;

3. High efficiency;

4. Reliability and durability;

5. Easy to manage and maintain;

6. Transportability;

7. Small dimensions;

8. Safety at work;

Reliability- this is the ability of a part to maintain its performance characteristics and perform specified functions during a specified service life.

Requirements for machine parts:

A) strength– the resistance of the part to destruction or the occurrence of plastic deformation during the warranty period;

b ) rigidity– guaranteed degree of resistance to elastic deformation of the part during its operation;

V ) wear resistance– resistance of the part: to mechanical wear or corrosion-mechanical wear;

G) small dimensions and weight;

e) made from inexpensive materials;

e) manufacturability(production should be carried out with the least amount of labor and time);

and) safety;

h) compliance with state standards.

When calculating parts for strength, it is necessary to obtain a stress in a dangerous section that will be less than or equal to the permissible one: δ max ≤[δ];

τ max ≤[τ] Allowable voltage

- this is the maximum operating voltage that can be allowed in a dangerous section, provided that the necessary strength and durability of the part is ensured during its operation.

;
The permissible voltage is selected depending on the maximum voltage

n is the permissible safety factor, which depends on the type of structure, its responsibility, and the nature of the loads.

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VOCATIONAL SCHOOL No. 22

Abstract on the discipline

"Technical mechanics"

on the topic: “Machine parts: concept and their characteristics”

Completed by: Rozhko Svetlana

Saratov-2010

Basic definitions and concepts

A part is a product obtained from a material of a homogeneous brand without assembly operations.

Assembly unit - a product obtained using assembly operations.

A mechanism is a complex of parts and assembly units created for the purpose of performing a certain type of movement of the driven link with a predetermined movement of the leading link.

A machine is a set of mechanisms created for the purpose of converting one type of energy into another, or to perform useful work, in order to facilitate human labor.

Mechanical transmissions.

Gears are mechanisms designed to transmit movement.

1. According to the method of transmission of motion:

a) gearing (gear, worm, chain);

b) friction (friction);

2. By method of contact:

a) direct contact (tooth, worm, friction);

b) using a transmission link.

Gear - consists of a gear and gear wheel and is designed to transmit rotation.

Advantages: reliability and durability, compactness.

Disadvantages: noise, high requirements for manufacturing and installation precision, depressions are stress concentrators.

Classification.

1. Cylindrical (11 axes), conical (crossed axes), screw (crossed axes).

2. According to the tooth profile:

a) involute;

b) cycloidal;

c) with a Novikov link.

3. According to the method of engagement:

a) internal;

b) external.

4. According to the location of the teeth:

a) straight toothed;

b) helical;

c) mevron.

5. By design:

a) open;

b) closed.

Used in machine tools, cars, watches.

A worm gear consists of a worm and a worm wheel, the axes of which are crossed. Serves to transmit rotation wheel.

Advantages: reliability and durability, the ability to create self-braking transmission, compactness, smooth and silent operation, the ability to create large subordinate numbers.

Disadvantages: low speed, high transmission heating, use of expensive anti-friction materials.

Classification.

1. By type of worm:

a) cylindrical;

b) globoidal.

2. According to the profile of the worm tooth:

a) involute;

b) covolutes;

c) Archimedes.

3. By number of visits:

a) single-pass;

b) Multi-pass.

4. In relation to the worm to the worm wheel:

a) with the bottom;

b) with the top;

c) with the side.

Used in machines and lifting devices.

A belt drive consists of pulleys and a belt. Serves to transmit rotation over a distance of up to 15 meters.

Advantages: smooth and quiet operation, simplicity of design, possibility of smooth adjustment of the gear ratio.

Disadvantages: belt slippage, limited belt service life, need for tensioners, impossibility of use in explosive environments.

It is used in conveyors, machine drives, in the textile industry, and in sewing machines.

Instrumentation.

Belts - leather, rubber.

Pulleys - cast iron, aluminum, steel.

A chain drive consists of a chain and gears. Serves to transmit torque over a distance of up to 8 meters.

Advantages: reliability and strength, no slippage, less pressure on shafts and bearings.

Disadvantages: noise, high wear, sagging, difficult lubricant supply.

Material - steel.

Classification.

1. By purpose:

a) freight,

b) tension,

c) traction.

2. By design:

a) roller,

b) bushings,

c) toothed.

They are used in bicycles, machine and car drives, and conveyors.

Shafts and axles.

A shaft is a part designed to support other parts in order to transmit torque.

During operation, the shaft experiences bending and torsion.

An axis is a part intended only to support other parts mounted on it; during operation, the axis only experiences bending.

Classification of shafts.

1. By purpose:

a) straight,

b) cranked,

c) flexible.

2. According to the form:

a) smooth,

b) stepped.

3. By section:

a) solid,

Shaft elements. Shafts are often made of steel-20, steel 20x.

Shaft calculation: kr=|Mmax|\W<=[ кр] и=|Mmax|W<=[ и] Оси только на изгиб. W - момент сопротивления сечения [м3].

Clutches are devices designed to connect shafts to transmit torque and ensure stopping of the unit without turning off the engine, as well as protecting the operation of the mechanism during overloads.

Classification.

1. Non-detachable:

a) hard

b) flexible.

Advantages: simplicity of design, low cost, reliability.

Disadvantages: can connect shafts of the same diameters.

Material: steel-45, gray cast iron.

2. Managed:

a) toothed

b) friction.

Advantages: simplicity of design, different shafts, the mechanism can be turned off when overloaded.

3. Self-acting:

a) safety,

b) overtaking,

c) centrifugal.

Advantages: reliable operation, transmits rotation when a certain rotation speed is reached due to inertial forces.

Disadvantages: complexity of the design, high wear of the cams.

Made from gray cast iron.

4. Combined.

Couplings are selected according to the GOST table.

Permanent connections

Permanent connections are those connections of parts that cannot be disassembled without destroying the parts included in this connection.

These include: riveted, welded, soldered, adhesive joints.

Riveted connections.

Riveted connections:

1. By purpose:

a) durable

b) dense.

2. According to the location of the rivets:

a) parallel,

b) in a checkerboard pattern.

3. By number of visits:

a) single row,

b) multi-row.

Advantages: they withstand shock loads well, are reliable and durable, provide visual contact for the quality of the seam.

Disadvantages: holes are stress concentrators and reduce the tensile strength, make the structure heavier, noisy production.

Welding connections

Welding is the process of joining parts by heating them to the melting temperature, or by plastic deformation in order to create a permanent connection.

a) gas,

b) electrode,

c) contact,

d) laser,

d) cold,

e) explosion welding.

Welded connections:

a) angular,

b) butt,

c) overlap,

d) T-bar,

d) point.

Advantages: provides a reliable sealed connection, the ability to connect any materials of any thickness, silent process.

Disadvantages: changes in physical and chemical properties in the weld area, warping of the part, difficulty in checking the quality of the seam, requires highly qualified specialists, does not withstand repeated variable loads, the seam is a stress concentrator.

Adhesive connections.

Advantages: does not weigh down the structure, low cost, does not require specialists, the ability to connect any parts of any thickness, noiseless process.

Disadvantages: “aging” of the glue, low heat resistance, the need for preliminary cleaning of the surface.

All permanent connections are designed for shear.

Тср=Q\A<=[Тср].

Threads (classification)

1. By purpose:

a) fastenings,

b) running gear,

c) sealing.

2. According to the angle at the apex:

a) metric(60),

b) inch (55).

3. By profile:

a) triangular,

b) trapezoidal,

c) stubborn

d) round,

d) rectangular.

4. By number of visits:

a) single-pass,

b) multi-pass.

5. In the direction of the helix:

a) left, part mechanism permanent connection

b) right.

6. On the surface:

a) external,

b) internal,

c) cylindrical,

d) conical.

Threaded surfaces can be made:

a) manually,

b) on machines,

c) on automatic rolling machines.

Advantages: simplicity of design, reliability and strength, standardization and interchangeability, low cost, does not require specialists, the ability to connect any materials.

Disadvantages: thread is a stress concentrator, wear of contacting surfaces. Material - steel, non-ferrous alloys, plastic.

Keyed connections.

Keys are: prismatic, segmental, wedge.

Advantages: simplicity of design, reliability in operation, long keys - guides.

Disadvantages: the keyway is a stress concentrator.

Spline connections.

There are: straight-sided, triangular, involute.

Advantages: reliable operation, uniform distribution over the entire cross-section of the shaft.

Disadvantages: difficult to manufacture.

R=sqr(x^2+y^2) - for fixed supports,

in x - cos of a given angle

by y - sin of this angle or cos (90-angle)

if the larger side of the triangle then take 2/3

if small then - 1/3

d'Alembert principle: F+R+Pu=0

Literature

Textbooks and tutorials

1. Yablonsky A.A., Nikiforova V.M. Course of theoretical mechanics. Part 1, 2 Publishing house "Higher School", M.: 1996

2.Voronkov I.M. Course of theoretical mechanics. State publishing house of technical and theoretical literature. M: 2006

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Machine parts (from French détail - detail)

elements of machines, each of which is a single whole and cannot be disassembled into simpler, component parts of machines without destruction. Mechanical engineering is also a scientific discipline that deals with the theory, calculation, and design of machines.

The number of parts in complex machines reaches tens of thousands. The manufacture of machines from parts is primarily caused by the need for relative movements of the parts. However, fixed and mutually fixed parts of machines (links) are also made from separate parts connected to each other. This makes it possible to use optimal materials, restore the functionality of worn-out machines, replacing only simple and cheap parts, facilitates their manufacture, and ensures the possibility and convenience of assembly.

D. m. as a scientific discipline considers the following main functional groups.

Body parts ( rice. 1 ), bearing mechanisms and other machine components: plates supporting machines, consisting of individual units; frames carrying the main components of machines; frames of transport vehicles; housings of rotary machines (turbines, pumps, electric motors); cylinders and cylinder blocks; gearbox housings; tables, slides, supports, consoles, brackets, etc.

Transmissions are mechanisms that transmit mechanical energy over a distance, as a rule, with the transformation of speeds and moments, sometimes with the transformation of types and laws of motion. Rotary motion transmissions, in turn, are divided according to the principle of operation into gear transmissions that operate without slipping - gear transmissions (See Gear transmission) ( rice. 2 , a, b), worm gears (See Worm gear) ( rice. 2 , c) both chain and friction drives - belt drives (See Belt drive) and friction drives with rigid links. Based on the presence of an intermediate flexible link, which allows for significant distances between the shafts, a distinction is made between flexible transmissions (belt and chain) and direct contact transmissions (gear, worm, friction, etc.). According to the relative arrangement of the shafts - transmissions with parallel axes of shafts (cylindrical gears, chain, belt), with intersecting axes (bevel gears), with intersecting axes (worm, hypoid). According to the main kinematic characteristic - the gear ratio - there are transmissions with a constant gear ratio (reducing, increasing) and with a variable gear ratio - stepped (gearboxes (See Gearbox)) and continuously variable (CVTs). Gears that convert rotational motion into continuous translational motion or vice versa are divided into screw - nut (sliding and rolling) gears, rack - rack and pinion, rack - worm, long half-nut - worm.

Shafts and axles ( rice. 3 ) are used to support rotating engines. There are gear shafts, load-bearing parts of gears - gears, pulleys, sprockets, and main and special shafts, which, in addition to gear parts, carry working parts of engines or implements. Axles, rotating and stationary, are widely used in transport vehicles to support, for example, non-driving wheels. Rotating shafts or axles rest on the Bearing and ( rice. 4 ), and progressively moving parts (tables, supports, etc.) move along guides (See Guides). Sliding bearings can work with hydrodynamic, aerodynamic, aerostatic friction or mixed friction. Ball bearings are used for small and medium loads, roller bearings for heavy loads, and needle bearings for tight spaces. Rolling bearings are most often used in machines; they are manufactured in a wide range of outer diameters from one mm up to several m and weight from fractions G up to several T.

Couplings are used to connect the shafts. (See Clutch) This function can be combined with compensation for manufacturing and assembly errors, mitigation of dynamic effects, control, etc.

Elastic elements are intended to insulate vibrations and dampen impact energy, to perform engine functions (for example, clock springs), to create gaps and tension in mechanisms. There are coil springs, coil springs, leaf springs, rubber springs, etc.

Connecting parts are a separate functional group. There are: permanent connections (See Permanent connection), which do not allow separation without destruction of parts, connecting elements or connecting layer - welded ( rice. 5 , A), soldered, riveted ( rice. 5 , b), adhesive ( rice. 5 , c), rolled; detachable connections (See Detachable connection), allowing separation and carried out by the mutual direction of the parts and frictional forces (most detachable connections) or only by mutual direction (for example, connections with parallel keys). According to the shape of the connecting surfaces, connections are distinguished by planes (most) and by surfaces of rotation - cylindrical or conical (shaft - hub). Welded joints are widely used in mechanical engineering. Of the detachable connections, the most common are threaded connections made with screws, bolts, studs, nuts ( rice. 5 , G).

The prototypes of many mechanical tools have been known since ancient times, the earliest of them being the lever and the wedge. More than 25 thousand years ago, people began to use springs in bows to throw arrows. The first flexible link transmission was used in a bow drive for making fire. Rollers, the operation of which is based on rolling friction, were known more than 4,000 years ago. The first parts that approach modern operating conditions include the wheel, axle and bearing in carts. In ancient times, and during the construction of temples and pyramids, Gates and Blocks were used. Plato and Aristotle (4th century BC) mention in their writings metal axles, gear wheels, cranks, rollers, and pulleys. Archimedes used a screw in a water-lifting machine, apparently known earlier. The notes of Leonardo da Vinci describe helical gears, gears with rotating pins, rolling bearings and hinge chains. In the literature of the Renaissance there is information about belt and rope transmissions, cargo screws, and couplings. D. m. designs have been improved, and new modifications have appeared. At the end of the 18th - beginning of the 19th centuries. Riveted connections have become widespread in boilers and railway structures. bridges, etc. In the 20th century riveted connections were gradually replaced by welded ones. In 1841, J. Whitworth in England developed a system of fastening threads, which was the first work on standardization in mechanical engineering. The use of flexible transmissions (belt and rope) was caused by the distribution of energy from a steam engine along the factory floors, driving transmissions, etc. With the development of individual electric drives, belt and rope drives began to be used to transmit energy from electric motors and prime movers in the drives of light and medium-sized machines. In the 20s 20th century V-belt drives became widespread. A further development of flexible transmissions are multi-V-belts and timing belts. Gear transmissions were continuously improved: pinion gearing and engagement of a straight-sided profile with roundings were replaced by cycloidal, and then involute. An essential stage was the appearance of M. L. Novikov’s circular helical gearing. Since the 70s of the 19th century. Rolling bearings began to be widely used. Hydrostatic bearings and guides, as well as air-lubricated bearings, have become widespread.

D. materials to a large extent determine the quality of cars and make up a significant part of their cost (for example, in cars up to 65-70%). The main materials for metalworking are steel, cast iron, and non-ferrous alloys. Plastics are used as electrical insulating, antifriction and friction, corrosion-resistant, heat-insulating, high-strength (fiberglass), and also as having good technological properties. Rubbers are used as materials with high elasticity and wear resistance. Important mechanical components (gears, highly stressed shafts, etc.) are made of hardened or tempered steel. For machine tools, the dimensions of which are determined by rigidity conditions, materials are used that allow the production of parts of perfect shapes, for example, unhardened steel and cast iron. D. m., operating at high temperatures, are made of heat-resistant or heat-resistant alloys. The highest nominal stresses from bending and torsion, local and contact stresses, and wear also occur on the surface of the metal; therefore, the metal is subjected to surface hardening: chemical-thermal, thermal, mechanical, and thermo-mechanical treatment.

Devices must, with a given probability, be operational during a certain service life at the minimum required cost of their manufacture and operation. To do this, they must satisfy performance criteria: strength, rigidity, wear resistance, heat resistance, etc. Calculations for the strength of structural steel under variable loads can be carried out using nominal stresses, safety factors taking into account stress concentration and scale factor, or taking into account operating mode variability. The most reasonable can be considered the calculation based on a given probability and failure-free operation. The calculation of mechanical rigidity is usually carried out based on the condition of satisfactory operation of the mating parts (the absence of increased edge pressures) and the operating conditions of the machine, for example, the production of precision products on a machine. To ensure wear resistance, they strive to create conditions for liquid friction, in which the thickness of the oil layer must exceed the sum of the heights of microroughnesses and other deviations from the correct geometric shape of the surfaces. If it is impossible to create fluid friction, pressure and speed are limited to those established in practice or wear is calculated based on similarity according to operational data for components or machines for the same purpose. Mechanical engineering calculations are developing in the following directions: computational optimization of structures, the development of computer calculations, the introduction of the time factor into calculations, the introduction of probabilistic methods, standardization of calculations, and the use of tabular calculations for centralized mechanical engineering. The foundations of the theory of dynamic mechanical calculations were laid by research in the field of gearing theory (L. Euler, Kh. I. Gokhman), the theory of friction of threads on drums (L. Euler and others), and the hydrodynamic theory of lubrication (N. P. Petrov, O. Reynolds, N. E. Zhukovsky, etc.). Research in the field of mechanical engineering in the USSR is carried out at the Institute of Mechanical Engineering, the Research Institute of Mechanical Engineering Technology, and the Moscow Higher Technical University named after. Bauman and others. The main periodical publication in which materials on the calculation, design, and application of mechanical engineering are published is the Bulletin of Mechanical Engineering.

The development of mechanical design is taking place in the following directions: increasing the parameters and developing high parameters of mechanical motors, using the optimal capabilities of mechanical devices with solid links, hydraulic, electrical, electronic and other devices, and designing motors for the period before obsolescence. machines, increasing reliability, optimizing shapes in connection with new technology capabilities, ensuring perfect friction (liquid, gas, rolling), sealing joints of machine tools, making machines operating in an abrasive environment from materials whose hardness is higher than the hardness abrasives, standardization and organization of centralized production.

Lit.: Machine parts. Atlas of structures, ed. D. N. Reshetova, 3rd ed., M., 1968; Machine parts. Directory, vol. 1-3, M., 1968-69.

D. N. Reshetov.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what “Machine parts” are in other dictionaries:

A set of structural elements and their combinations, which represents the basis of the design of the machine. A machine part is a part of a mechanism that is manufactured without assembly operations. Machine parts is also scientific and... Wikipedia

machine parts- - Topics oil and gas industry EN machine components ... Technical Translator's Guide

1) dept. components and their simplest connections in machines, instruments, devices, fixtures, etc.: bolts, rivets, shafts, gears, keys, etc. 2) Scientific. a discipline that includes theory, calculation and design... Big Encyclopedic Polytechnic Dictionary

This term has other meanings, see Key. Installation of a key in a shaft groove Key (from Polish szponka, through German Spon, Span sliver, wedge, lining) an oblong-shaped part of machines and mechanisms inserted into the groove ... ... Wikipedia